The present invention generally relates to an ink jet printer capable of jetting ink droplets having different sizes from the same nozzle. More specifically, the present invention is directed to such an ink jet printer capable of jetting a plurality of ink droplets during a single printing time period.
As output apparatus of computers, color ink jet printers have been popularized in which several colors of ink are jetted from printing heads. To print out images processed by computers and the like in multi-color multi-gradation modes, these color ink jet printers have been widely employed.
An ink jet printer contains a printing head equipped with a large number of nozzles arranged in a sub-scanning direction (namely, paper feeding direction). While this printing head is moved by a carriage mechanism along a main scanning direction, a predetermined paper feeding operation is carried out along the above-described sub-scanning direction, so that a desirable print result is obtained. Based upon dot pattern data generated by converting printing data supplied from a host computer, ink droplets are jetted from the respective nozzles of the printing head at preselected timing. Then, the respective ink droplets are impacted onto a recording medium such as recording paper, and are adhered thereon, so that a printing operation is carried out. As previously described, since the ink jet printer determines as to whether or not the ink droplets are jetted, namely executes ON/OFF controls of dots, this ink jet printer cannot directly print out half-tone gradation such as a gray color.
Under such a circumstance, there have been utilized ink jet printers capable of controlling variably diameters of recording dots in such a manner that a plurality of ink droplets having different ink weights are jetted from the same nozzle. For instance, in such an ink jet printer described in Japanese Patent Publication No. 10-81013A, while a drive signal which is outputted every one printing time period is constituted by a plurality of drive pulses, at least one of drive pulses is selected based upon such printing data containing pulse selection signals corresponding to the respective drive pulses. In other words, in the related ink jet printer described in the publication, for example, the drive signal outputted every one printing time period is constituted by four drive pulses made of a first pulse (middle dot), a second pulse (small dot), a third pulse (middle dot), and a fourth pulse (meniscus vibration). While 1-bit data is allocated with respect to each of these drive pulses, jetting data is constructed. Then, in the case that a gradation value xe2x80x9c1xe2x80x9d of non-dot is realized, xe2x80x9c0xe2x80x9d is applied to a switcher for a time period during which the first to third pulses are generated. On the other hand, xe2x80x9c1xe2x80x9d is applied to the switcher in synchronism with the generation of the fourth pulse in order that only the fourth pulse for vibrating a meniscus of ink in the nozzle is applied to a piezoelectric vibrator. As a result, the gradation value xe2x80x9c1xe2x80x9d of the non-dot may be realized in which an ink droplet is not jetted. To this end, after the 2-bit data (00) indicative of the gradation value 1 has been decoded into the 4-bit data (0001) by a decoder, the decoded 4-bit data is applied to the above-described switcher.
Similarly, in the case that the gradation value 2 of the small dot is realized, xe2x80x9c0xe2x80x9d is applied to the switcher for a time period during which the first pulse, the third pulse, and the fourth pulse are generated. On the other hand, when xe2x80x9c1xe2x80x9d is applied to the switcher in synchronism with the generation of the second pulse, only the second pulse is applied to the piezoelectric vibrator, so that the gradation value 2 can be realized by which the ink droplets equivalent to the small dot are jetted. In this case, after 2-bit data (01) indicative of the gradation value 2 is decoded into 4-bit data (0100) by the decoder, the decoded 4-bit data is applied to the above-explained switcher.
Similarly, in the case that the gradation value 3 of one middle dot is realized, xe2x80x9c0xe2x80x9d is applied to the switcher for a time period during which the second pulse, the third pulse, and the fourth pulse are generated. On the other hand, when xe2x80x9c1xe2x80x9d is applied to the switcher in synchronism with the generation of the first pulse, only the first pulse is applied to the piezoelectric vibrator, so that the gradation value 3 can be realized by which the ink droplets equivalent to the middle dot are jetted. In this case, after 2-bit data (10) indicative of the gradation value 3 is decoded into 4-bit data (1000) by the decoder, the decoded 4-bit data is applied to the above-explained switcher.
Similarly, in the case that the gradation value 4 of two middle dots is realized, xe2x80x9c0xe2x80x9d is applied to the switcher for a time period during which the second pulse, and the fourth pulse are generated. On the other hand, when xe2x80x9c1xe2x80x9d is applied to the switcher in synchronism with the generations of the first and third pulses, only the first and third pulses are applied to the piezoelectric vibrator, so that the gradation value 4 can be realized by which the ink droplets equivalent to the middle dot are jetted two times. In this case, these ink droplets are continuously impacted onto the recording paper, and these ink droplets are mixed with each other, so that actually one large dot may be formed. Accordingly, the gradation value 4 can be realized. In this case, after 2-bit data (11) indicative of the gradation value 4 is decoded into 4-bit data (1010) by the decoder, the decoded 4-bit data is applied to the above-explained switcher.
On the other hand, in a head drive circuit mounted in the printing head of the ink jet printer, transmission gates (will be referred to as xe2x80x9cTGxe2x80x9d hereinafter) are provided in correspondence with every nozzle row used to jet each of the color ink droplets, while these TGs are constructed of switchers used to supply drive signals to the piezoelectric vibrators.
In order to execute the above-described dot gradation, for example, 2-bit gradation (multi-gradation) data (00, 01, 10, 11) SI is required to be decoded into such a pulse selection signal which is made of 4-bit data (0001, 0100, 1000, 1010). Thus, both this 2-bit gradation data (jetting data) SI and program data (pattern data) SP for executing this decoding must be supplied to the switcher (TG) incorporated in the printing head.
In the related ink jet printer, the jetting data (00, 01, 10, 11) SI is supplied from a control unit incorporated in a printer main body into the switcher (TG) incorporated in the printing head with respect to each of the color nozzle rows (each of color TGs). On the other hand, as to the program data (pattern data) SP, commonly-used patterns are supplied to all of the color nozzle rows (each of color TGs).
In the related ink jet printer, since the jetting data SI for each of these color nozzle rows (namely, respective color TGs) is supplied to the switcher (TG) incorporated in the printing head from the control unit of the printer main body, signal lines for the jetting data SI for each of these color nozzle rows (respective color TGs) are required within an FFC (Flexible Flat Cable) which electrically connects the printer main body to the printing head. Furthermore, at least one signal line for the pattern data SP is required in this FFC.
To achieve higher printing speeds and also higher image qualities in ink jet printers, the following measure may be conceived. That is, nozzle rows (TGs) for the respective colors incorporated in printing heads are increased. As explained above, when a plurality of ICs (TGs) are mounted on the printing heads, a plurality of signal lines are furthermore required in correspondence with these plural ICs.
However, a plurality of such signal lines are required within the FFC, so that the width of this FFC would be widened, and thus, wire routing works would become difficult. In addition, since such signal lines are provided with respect to each of these TGs, if a total number of TGs is increased, then manufacturing cost thereof is accordingly increased.
Also, in the related ink jet printer, as to the program data (pattern data) SP, the commonly-used patterns are supplied to all of the color nozzle rows (respective color TGs). As a result, it is practically difficult to control the ink jetting amounts for the respective colors within a single printing time period, for instance, it is practically difficult to make the monochrome dot gradation pattern different from the color dot gradation pattern.
It is therefore a first object of the present invention to provide an ink jet printer capable of representing multi-gradations by using both jetting data and pattern data, and also capable of being manufactured in relatively low cost as well as realizing easy wire routing works of an FFC by reducing a total number of signal lines connected between a printer main body and a printing head.
A second object of the present invention is to provide such an ink jet printer capable of realizing a high-density printing operation and also a printing operation with a high image quality by controlling ink jetting amounts of respective colors within a single printing time period, for instance, by making monochrome dot gradation pattern different from color dot gradation pattern.
A third object of the present invention is to achieve the second object without increasing a total number of signal lines incorporated in the FFC.
In order to achieve the above objects, according to the present invention, there is provided an ink jet printer, comprising:
a control unit, which converts externally provided printing data into jetting data associated with a size of dot to be printed;
a drive signal generator, which generates a drive signal including a plurality of drive pulses;
a printing head, which includes:
a pressure chamber communicated with a nozzle;
a pressure generating element, which varies pressure inside of the pressure chamber when at least one of the drive pulses is applied;
a decoder, which decodes the jetting data into pulse select information in accordance with a predetermined conversion relationship; and
a switcher, which selects at least one of the drive pulses to be applied to the pressure generating element in accordance with the pulse select information;
pattern data, which defines the conversion relationship; and
a common signal line, which transfers the jetting data and the pattern data from the control unit to the printing head.
Preferably, the pattern data is made continuous with the jetting data.
According to the present invention, there is also provided an ink jet printer, comprising:
a control unit, which converts externally provided printing data into jetting data associated with a size of dot to be printed;
a drive signal generator, which generates a drive signal including a plurality of drive pulses;
a printing head, which includes:
at least two nozzle rows, each associated with at least one color of ink and including a plurality of nozzles each communicated with a pressure chamber;
a pressure generating element, which varies pressure inside of the pressure chamber when at least one of the drive pulses is applied;
a decoder, which decodes the jetting data into pulse select information in accordance with a predetermined conversion relationship; and
a switcher, which selects at least one of the drive pulses to be applied to the pressure generating element in accordance with the pulse select information; and
at least two pattern data, each associated with at least one color of ink different from one another and each defining the conversion relationship.
Preferably, the pattern data is made continuous with the jetting data.
Preferably, the ink jet printer further comprises a common signal line, which transfers the jetting data and the pattern data from the control unit to the printing head.
Preferably, the drive signal includes a first drive pulse associated with a first amount of jetted ink, a second drive pulse associated with a second amount of jetted ink which is less than the first amount, and a third drive pulse associated with the first amount of jetted ink. Here, at least one of the plural dot pattern data is so constructed as to select either one of the first drive pulse and the third drive pulse within a unit printing time period.
In the above configurations, since the pattern data is transferred by way of the signal line which is commonly used with the jetting data from the control unit to the printing head, such a signal line used to transfer the pattern data need not be separately provided. As a consequence, for instance, a total number of signal lines incorporated in the FFC can be reduced. While the ink jet printer can be manufactured in relatively low cost, wire routing works of this FFC can be easily made.
In addition, as to at least one color, since such pattern data which is different from that of another color is employed, the programmable ink jetting control operation can be carried out in the ink jet printer, for instance, the resolution of this relevant one color may be made different from the resolution of another color.